mirrors/cosmopolitan
1
0
Fork 0
mirror of https://github.com/jart/cosmopolitan.git synced 2025-06-30 16:28:30 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Add posix semaphores support

Browse source 
There's still some bugs to work out on Windows and OpenBSD.
This commit is contained in:
Justine Tunney 2022-10-14 08:25:47 -07:00
parent f52f65b2e3
commit 8111462789
No known key found for this signature in database
GPG key ID: BE714B4575D6E328
36 changed files with 779 additions and 59 deletions
Download patch file Download diff file Expand all files Collapse all files

113
libc/thread/sem_timedwait.c Normal file
View file

@ -0,0 +1,113 @@
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/calls/struct/timespec.h"
#include "libc/calls/struct/timespec.internal.h"
#include "libc/errno.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/strace.internal.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/semaphore.h"
#include "libc/thread/semaphore.internal.h"
#include "third_party/nsync/futex.internal.h"
static void sem_delay(int n) {
volatile int i;
for (i = 0; i != 1 << n; i++) donothing;
}
// TODO(jart): This should be abstracted by polyfill.
static struct timespec *sem_timeout(struct timespec *memory,
const struct timespec *abstime) {
struct timespec now;
if (!abstime) {
return 0;
} else if (FUTEX_TIMEOUT_IS_ABSOLUTE) {
*memory = *abstime;
return memory;
} else {
now = _timespec_real();
if (_timespec_cmp(now, *abstime) > 0) {
*memory = (struct timespec){0};
} else {
*memory = _timespec_sub(*abstime, now);
}
return memory;
}
}
/**
* Locks semaphore w/ deadline.
*
* @param abstime is absolute deadline or null to wait forever
* @return 0 on success, or -1 w/ errno
* @raise EINTR if signal was delivered instead
* @raise EDEADLK if deadlock was detected
* @raise ETIMEDOUT if deadline expired
* @raise EINVAL if `sem` is invalid
*/
int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
int e, i, v, rc;
struct timespec ts;
e = errno;
for (i = 0; i < 7; ++i) {
rc = sem_trywait(sem);
if (!rc) {
return rc;
} else if (errno == EAGAIN) {
errno = e;
sem_delay(i);
} else {
return rc;
}
}
do {
if (!(v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed))) {
rc = nsync_futex_wait_(&sem->sem_value, v, sem->sem_pshared,
sem_timeout(&ts, abstime));
if (rc == -EINTR) {
rc = eintr();
} else if (rc == -EAGAIN || rc == -EWOULDBLOCK) {
rc = 0;
} else if (rc == -ETIMEDOUT) {
_npassert(abstime);
if (_timespec_cmp(*abstime, _timespec_real()) <= 0) {
rc = etimedout();
} else {
rc = 0;
}
} else {
_npassert(!rc);
rc = 0;
}
} else if (v > 0) {
rc = 0;
} else {
rc = einval();
}
} while (!rc && (!v || !atomic_compare_exchange_weak_explicit(
&sem->sem_value, &v, v - 1, memory_order_acquire,
memory_order_relaxed)));
STRACE("sem_timedwait(%p, %s) → %d% m", sem, DescribeTimespec(0, abstime),
rc);
return rc;
}